*{
  margin:0;
  padding:0;
}

.rectangle{
  width:370px;
  margin:50px auto;
  font-size:1.1em;
}

input,label,span{
  margin:5px 0;
  font-size:1em;
  padding-left:5px;
}

input:invalid+span:after{
  content:'✖';
  color:red;

}

input:valid+span:after{
  content: '✓';
  color:green;
}

#calc{
  margin-left:63px;
  width:70px;
}

span{
  color:red;
}

#height-val,#width-val{
  color:red;
  margin-left:83px;
  font-size:0.8em;
}

